US20130057376A1 - Ferrite ceramic composition, ceramic electronic component, and process for producing ceramic electronic component - Google Patents

Ferrite ceramic composition, ceramic electronic component, and process for producing ceramic electronic component Download PDF

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US20130057376A1
US20130057376A1 US13/601,842 US201213601842A US2013057376A1 US 20130057376 A1 US20130057376 A1 US 20130057376A1 US 201213601842 A US201213601842 A US 201213601842A US 2013057376 A1 US2013057376 A1 US 2013057376A1
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coil
coil conductor
ceramic
electronic component
mol
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Atsushi Yamamoto
Akihiro Nakamura
Wataru KANAMI
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Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B18/00—Layered products essentially comprising ceramics, e.g. refractory products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
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    • H01F1/34—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites
    • H01F1/342—Oxides
    • H01F1/344—Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4
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    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
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    • C04B2235/3262—Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
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Definitions

  • the technical field relates to a ferrite ceramic composition, a ceramic electronic component, and a process for producing the ceramic electronic component, and more specifically relates to a ferrite ceramic composition which can be fired simultaneously with an electrically conductive material containing Cu as the main component, a ceramic electronic component (e.g., a common mode choke coil) which is produced using the ferrite ceramic composition, and a process for producing the ceramic electronic component.
  • a ferrite ceramic composition which can be fired simultaneously with an electrically conductive material containing Cu as the main component, a ceramic electronic component (e.g., a common mode choke coil) which is produced using the ferrite ceramic composition, and a process for producing the ceramic electronic component.
  • common mode choke coils have been used widely for reducing common mode noises generated between signal lines or power supply lines and GND (ground) lines in various electronic devices.
  • noise components are transmitted in a common mode and signal components are transmitted in a normal mode.
  • noises are reduced by separating from signals.
  • JP 2958523 B1 proposes a laminate-type common mode choke coil which comprises a sintered laminate 105 that is produced by laminating multiple insulating material layers 101 , 102 and multiple coil conductors 103 a to 103 d , 104 a to 104 d on each other to form at least two coils 106 , 107 .
  • the coil conductors 103 a to 103 d , 104 a to 104 d are produced such that they are electrically connected and are magnetically coupled to each other.
  • the at least two coils 106 , 107 are arranged in the direction of the lamination of the sintered laminate 105 , and a distance d between adjacent two of the coil conductors that constitute the coils 106 , 107 is adjusted to a smaller value than a distance D between the adjacent coils.
  • JP 7-45932 Y proposes a common mode choke coil produced by laminating an approximately square first magnetic sheet and an approximately square second magnetic sheet alternately, wherein a substantially one turn ring-shaped electrically conductive pattern having a starting end and a terminal end is formed around the first magnetic sheet to form a first coil and a substantially one turn ring-shaped electrically conductive pattern having a starting end and a terminal end is formed around the second magnetic sheet to form a second coil.
  • JP 7-45932 Y (claim 1, lines 30-42 on column 6 etc.), as illustrated in FIG. 8 , when a signal that is input to a section A of the first coil L 1 is output to a section B, a magnetic flux ⁇ is generated.
  • a magnetic flux ⁇ which has a direction opposite to the direction of the magnetic flux ⁇ is generated, because the second coil L 2 was wound in phase with the first coil L 1 .
  • the conductive body patterns are formed around the same core and in the same number of turns.
  • the magnetic flux ⁇ and the magnetic flux ⁇ generated by both of the coil L 1 and the coil L 2 have the same density.
  • the magnetic flux ⁇ and the magnetic flux ⁇ neutralize each other in the magnetic body. That is, the common mode choke coil cannot act as a choke coil against noises in a normal mode, and can act as a choke coil only against noises in a common mode.
  • the common mode choke coil disclosed in JP 7-45932 Y (claim 1, lines 30-42 on column 6 etc.) is produced by laminating the first magnetic sheet and the second magnetic sheet alternately, wherein the first and second coils are embedded in the magnetic body. Therefore, this type of common mode choke coil is called an “alternately-wound common mode choke coil”.
  • the present disclosure provides a ferrite ceramic composition that can have secured insulation performance and good electric properties when fired simultaneously with an electrically conductive material containing Cu as the main component, a ceramic electronic component (e.g., a common mode choke coil) that is produced using the ferrite ceramic composition, and a process for producing the ceramic electronic component.
  • a ceramic electronic component e.g., a common mode choke coil
  • a ferrite ceramic composition at least Fe, Mn, Ni and Zn, and is characterized in that a molar content of Cu contained in ferrite ceramic composition is 0 to 5 mol % in terms of CuO content and, when the molar content (x (mol %)) of Fe in the ferrite ceramic composition in terms of Fe 2 O 3 content and the molar content (y (mol %)) of Mn in the ferrite ceramic composition in terms of Mn 2 O 3 content are expressed by a coordinate point (x,y), the coordinate point (x,y) is located within an area bounded by coordinate points A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10), G (35,7.5) and H (25,7.5).
  • the molar content of Zn is 33 mol % or less in terms of ZnO content.
  • the molar content of Zn is 6 mol % or more in terms of ZnO content.
  • a ceramic electronic component in another aspect of the disclosure, includes a magnetic body part, a first coil conductor, and a second coil conductor which has substantially the same shape as that of the first coil conductor and of which the starting end and the terminal end are arranged with a predetermined distance apart from the first coil conductor.
  • the first coil conductor and the second coil conductor are embedded in the magnetic body part, each of the first coil conductor and the second coil conductor includes an electrically conductive material containing Cu as the main component, and the magnetic body part comprises any of the above-mentioned ferrite ceramic compositions.
  • the first and second coil conductors and the magnetic body part are fired simultaneously.
  • the firing is performed in an atmosphere having an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure for Cu—Cu 2 O.
  • a process for producing a ceramic electronic component includes a calcination step of precisely weighing an Fe compound, an Mn compound, a Cu compound, a Zn compound and an Ni compound in such a manner that the molar content of Cu becomes 0 to 5 mol % in terms of CuO content and, when the molar content (x (mol %)) of Fe in terms of Fe 2 O 3 content and the molar content (y (mol %)) of Mn in terms of Mn 2 O 3 content are expressed by a coordinate point (x,y), the coordinate point (x,y) is located within an area bounded by coordinate points A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10), G (35,7.5) and H (25,7.5), mixing the weighed components together, and calcining the mixture, thereby producing a calcined powder; a ceramic thin layer body production step of producing ceramic thin layer bodies from the
  • a via conductor for the second coil conductor, which is electrically isolated from the first coil pattern, is formed on the surface of each of the first-coil-pattern-formed ceramic thin layer bodies, and a via conductor for the first coil conductor, which is electrically isolated from the second coil pattern, is formed on the surface of each of the second-coil-pattern-formed ceramic thin layer bodies.
  • FIG. 1 is a view illustrating the content ranges of Fe 2 O 3 and Mn 2 O 3 for the ferrite ceramic composition according to an exemplary embodiment.
  • FIG. 2 is a perspective view illustrating an exemplary embodiment of a common mode choke coil as the ceramic electronic component.
  • FIG. 3 is an exploded top view illustrating the main part of the common mode choke coil shown in FIG. 2 .
  • FIG. 4 is a cross sectional view of a sample for the specific resistance measurement produced in Example 1.
  • FIG. 5 is a view illustrating the time course of the change in resistance value of a sample according to the present disclosure produced in Example 2 along with that of a sample produced in a comparative example which is out of the scope of the present disclosure.
  • FIG. 6 is a view illustrating the time course of the change in resistance decrease ratio of a sample according to the present disclosure produced in Example 2 along with that of a sample produced in a comparative example which is out of the scope of the present disclosure.
  • FIG. 7 is a cross sectional view illustrating a parallel-wound common mode choke coil which is disclosed in JP 2958523 B1 (claim 1, paragraph [0026] etc.).
  • FIG. 8 is a view illustrating the principle of operation of an alternately-wound common mode choke coil which is disclosed in JP 7-45932 Y (claim 1, lines 30-42 on column 6 etc.).
  • the performance of a common mode choke coil can be assessed by a coupling coefficient (an index representing the degree of the magnetic coupling between magnetically coupled coils). That is, the largest value for a coupling coefficient is “1”. The higher the coupling coefficient, the smaller the impedance value in a normal mode becomes and the smaller the influence on signals becomes.
  • a coupling coefficient an index representing the degree of the magnetic coupling between magnetically coupled coils. That is, the largest value for a coupling coefficient is “1”. The higher the coupling coefficient, the smaller the impedance value in a normal mode becomes and the smaller the influence on signals becomes.
  • the coupling coefficient is as low as up to about 0.2, because the coil 106 and the coil 107 are arranged apart from each other.
  • a higher coupling coefficient of 0.8 or more can be achieved, because the first magnetic sheet having the first coil pattern formed thereon and the second magnetic sheet having the second coil pattern formed thereon are laminated on each other. That is, it is believed that in principle, an alternately-wound common mode choke coil can provide high-performance noise reduction compared with a parallel-wound common mode choke coil.
  • Ni—Zn-based material which has been used widely in ferrite materials, is generally fired in an air atmosphere. Therefore, for firing such a magnetic material simultaneously with a coil conductor, an Ag-based material is used as the coil conductor material.
  • an Ag-based material is used as the coil conductor material.
  • an alternately-wound common mode choke coil as disclosed in JP 7-45932 Y (claim 1, lines 30-42 on column 6 etc.), the facing area is large between a first coil and a second coil, which is an area in which potential difference is produced. Further, an Ag-based material can be migrated readily. Therefore, an alternately-wound common mode choke coil might give rise to defects when being allowed to be left under a highly humid environment for a long period, and hardly acquires high reliability.
  • the content of ZnO is desirably 6 mol % or more when the magnetic permeability ⁇ of ferrite is taken into consideration.
  • the present disclosure provides a ferrite ceramic composition, ceramic electronic component and process for producing the ceramic electronic component that can address one or more of the above shortcomings. Embodiments consistent with the present disclosure will now be described in detail.
  • a ferrite ceramic composition according to the present disclosure has a spinel-type crystal structure represented by general formula X 2 O 3 .MeO, and contains at least Fe 2 O 3 and Mn 2 O 3 , which are trivalent element compounds, and ZnO and NiO, which are bivalent element compounds, and optionally contains CuO, which is a bivalent element compound.
  • the ferrite ceramic composition contains CuO at a molar content of 0 to 5 mol %, also contains Fe 2 O 3 and Mn 2 O 3 at such molar contents that, when the molar content of Fe 2 O 3 is expressed by x (mol %), the molar content of Mn 2 O 3 is expressed by y (mol %), and the molar content of Fe 2 O 3 and the molar content of Mn 2 O 2 are expressed by a coordinate point (x,y), the coordinate point (x,y) is located within a shaded area X defined by points A to H, as shown in FIG. 1 , wherein the remainder of the ferrite ceramic composition is made up by ZnO and NiO.
  • the coordinate points A to H correspond to the following molar contents: A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10), G (35,7.5) and H (25,7.5).
  • Ni—Zn-based ferrite when CuO, which has a melting point of as low as 1,026° C., is added to a ferrite magnetic composition, the ferrite magnetic composition can be fired at a lower temperature and the sintering properties can be improved.
  • the amount of CuO to be added is controlled in such a manner that the molar content of CuO becomes 5 mol % or less, i.e., 0 to 5 mol %.
  • the content of Fe 2 O 3 in the composition is smaller than the content defined in the stoichiometric composition, and Mn 2 O 2 is contained by substituting a portion of Fe by Mn, whereby the decrease in a specific resistance ⁇ can be avoided and insulation performance can be improved.
  • the ratio of X 2 O 3 (wherein X: Fe, Mn) to MeO (wherein Me: Ni, Zn, Cu) is 50:50 according to the stoichiometric composition, and X 2 O 3 and MeO are added at contents substantially defined in the stoichiometric composition.
  • a reductive atmosphere for Mn 2 O 2 can be achieved at a higher oxygen partial pressure than that for Fe 2 O 3 . Therefore, at an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure for Cu—Cu 2 O, the atmosphere for Mn 2 O 2 becomes strongly reductive compared that for Fe 2 O 3 . Therefore, the firing can be accomplished while reducing Mn 2 O 2 preferentially. That is, because Mn 2 O 2 is reduced preferentially than Fe 2 O 3 , the firing treatment can be accomplished before Fe 2 O 3 is reduced into Fe 2 O 4 .
  • the molar content of Mn 2 O 3 is less than 1 mol %, the molar content of Mn 2 O 3 is reduced excessively, and therefore Fe 2 O 3 can be reduced into Fe 3 O 4 more readily. As a result, the specific resistance ⁇ is decreased and satisfactory insulation performance cannot be secured.
  • the molar content of Fe 2 O 3 is 25 mol % or more but is less than 35 mol %, and in the case where the molar content of Fe 2 O 3 is 45 mol % or more but less than 47 mol %, if the molar content of Mn 2 O 3 exceeds 7.5 mol %, the decrease in a specific resistance ⁇ is caused and desired insulation performance cannot be secured.
  • the molar contents of Fe 2 O 3 and Mn 2 O 3 are controlled so as to fall within the area bounded by the coordinate points A to H shown in FIG. 1 .
  • the molar contents of ZnO and NiO are not particularly limited and can be set properly in accordance with the molar contents of Fe 2 O 3 , Mn 2 O 3 and CuO.
  • ZnO and NiO are added in such a manner that the molar content of ZnO becomes 6 to 33 mol % and the remainder is made up by NiO.
  • the content of ZnO is preferably 33 mol % or less.
  • ZnO has an effect of improving a magnetic permeability ⁇ . For achieving the effect, it is needed to add ZnO at a molar content of 6 mol %.
  • the molar content of ZnO is preferably 6 to 33 mol %.
  • the ferrite ceramic composition has a molar content of Cu of 0 to 5 mol % in terms of CuO content, and also has such molar contents of Fe and Mn that, when the molar content (x (mol %) of Fe in terms of Fe 2 O 3 content and the molar content (y (mol %)) of Mn in terms of Mn 2 O 3 content are expressed by a coordinate point (x,y), the coordinate point (x,y) is located within an area bounded by the coordinate points A to H. Therefore, when the ferrite ceramic composition is fired simultaneously with a Cu-based material, the specific resistance ⁇ is not decreased and desired insulation performance can be secured.
  • the molar content of ZnO is specified to 6 to 33 mol %, it becomes possible to produce a ceramic electronic component which has good magnetic permeability, in which a sufficient Curie point can be secured, and which can be operated securely under conditions including a high operation temperature.
  • FIG. 2 is a perspective view illustrating one embodiment of an alternately-wound common mode choke coil (simply referred to as a “common mode choke coil,” hereinafter) as the ceramic electronic component according to the present disclosure.
  • a common mode choke coil simply referred to as a “common mode choke coil,” hereinafter
  • first to fourth external electrodes 2 a to 2 d are formed on both end surfaces of a component body 1 .
  • the component body 1 includes a magnetic body part, a first coil conductor, and a second coil conductor which has substantially the same shape as that of the first coil conductor and of which the starting end and the terminal end are arranged with a predetermined distance apart from the first coil conductor.
  • the first coil conductor and the second coil conductor are embedded in the magnetic body part.
  • the starting end of the first coil conductor is electrically connected to the first external electrode 2 a
  • the terminal end of the first coil conductor is electrically connected to the second external electrode 2 b
  • the starting end of the second coil conductor is electrically connected to the third external electrode 2 c
  • the terminal end of the second coil conductor is electrically connected to the fourth external electrode 2 d.
  • each of the first and second coil conductors comprises an electrically conductive material containing Cu as the main component
  • the magnetic body part comprises the above-mentioned ferrite ceramic composition according to the present disclosure.
  • FIGS. 3A to 3I are an exploded top view of the component body 1 .
  • Fe 2 O 3 , ZnO, NiO, and optionally CuO are provided as the ceramic raw materials.
  • the ceramic raw materials are weighed precisely so as to have a CuO content of 0 to 5 mol % and such Fe 2 O 3 and Mn 2 O 3 contents that fulfill the specified area bounded by the coordinate points A to H.
  • the precisely weighed materials are introduced into a pot mill together with pure water and cobbled stones such as PSZ (partially stabilized zirconia) balls, the mixture is fully mixed and milled in a wet mode, and the milled product is evaporated to dryness and then calcined at a temperature of 700 to 800° C. for a predetermined time.
  • pure water and cobbled stones such as PSZ (partially stabilized zirconia) balls
  • the calcined powder is introduced into the pot mill again together with an organic binder such as polyvinyl butyral, an organic solvent such as ethanol and toluene and PSZ balls, and the resultant mixture is fully mixed and milled, thereby producing a ceramic slurry.
  • an organic binder such as polyvinyl butyral
  • an organic solvent such as ethanol and toluene and PSZ balls
  • the ceramic slurry is molded into a sheet-like form employing a doctor blade method or the like, thereby producing a magnetic ceramic green sheet (a ceramic thin layer body, simply referred to hereafter as “a magnetic material sheet,”) 3 a to 3 i having a predetermined thickness.
  • a magnetic ceramic green sheet a ceramic thin layer body, simply referred to hereafter as “a magnetic material sheet,”
  • a via hole is formed at a predetermined position using a laser processing machine.
  • an electrically conductive paste containing Cu as the main component (referred to hereinafter as a “Cu paste”) is prepared.
  • a first coil pattern 4 a , 4 b or a second coil pattern 5 a , 5 b is formed on each of the magnetic material sheets 3 c to 3 f by performing screen printing using the Cu paste, electrode patterns 6 a , 6 b , 7 a , 7 b are formed on the magnetic material sheets 3 b , 3 g , 3 h , and the via holes are filled with the above-mentioned electrically conductive paste. In this manner, via conductors 8 a to 8 e , 9 a to 9 f are produced.
  • FIGS. 3C to 3F illustrate the main body part of the coil conductor. Therefore, the steps illustrated in FIGS. 3C to 3F are repeated in accordance with the number of turns required.
  • the magnetic material sheets 3 b to 3 h thus produced are laminated together, outer-covering magnetic material sheets 3 a , 3 i are respectively arranged on both main surfaces, the resultant product is compressed by applying a pressure, and the compressed product is cut into a predetermined size, thereby producing a laminated molding.
  • the electrode pattern 6 a is electrically connected to the first coil pattern 4 a through the via conductor 8 a
  • the first coil pattern 4 a is connected to the first coil pattern 4 b through the via conductors 8 b , 8 c
  • the first coil pattern 4 b is connected to the electrode pattern 6 b through the via conductors 8 d , 8 e .
  • a first coil conductor is formed.
  • the electrode pattern 7 a is electrically connected to the second coil pattern 5 a through the via conductors 9 a , 9 b
  • the second coil pattern 5 a is connected to the second coil pattern 5 b through the via conductors 9 c , 9 d
  • the second coil pattern 5 b is connected to the electrode pattern 7 b through the via conductors 9 e , 9 f .
  • a second coil conductor is formed.
  • the first coil conductor and the second coil conductor are wound alternately, and the second coil conductor is embedded in the magnetic body part in such a manner that the starting end and the terminal end of the second coil conductor are arranged with a predetermined distance apart from the first coil conductor.
  • the laminated molding is fully defatted by heating under an atmosphere in which the oxidation of Cu does not occur, is introduced into a firing furnace of which the atmosphere is adjusted with an N 2 —H 2 —H 2 O mixed gas so as to have an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure for Cu—Cu 2 O, and is then fired at 900 to 1,050° C. for a predetermined time. In this manner, a component body 1 is produced.
  • an electrically conductive paste for external electrodes which contains Cu as the main component, is applied to side surfaces of the component body ( 1 ), and the applied electrically conductive paste is then dried and fired at 900° C., thereby forming first to fourth external electrodes 2 a to 2 d . In this manner, the above-mentioned common mode choke coil is produced.
  • the embodiment includes a calcination step of precisely weighing an Fe compound, an Mn compound, a Cu compound, a Zn compound and an Ni compound in such a manner that the molar content of Cu becomes 0 to 5 mol % in terms of CuO content and, when the molar content (x (mol %)) of Fe in terms of Fe 2 O 3 content and the molar content (y (mol %)) of Mn in terms of Mn 2 O 3 content are expressed by a coordinate point (x,y), the coordinate point (x,y) is located within a specific area, mixing the weighed components together, and calcining the mixture, thereby producing a calcined powder.
  • the embodiment includes a ceramic material sheet production step of producing ceramic material sheets 3 a to 3 i from the calcined powder, a first coil pattern formation step of forming first coil patterns by applying a Cu paste to the magnetic material sheets 3 c , 3 e , a second coil pattern formation step of forming second coil patterns 5 a , 5 b by applying the Cu paste to the magnetic material sheets 3 d , 3 f , a laminate formation step of alternately laminating a predetermined number of the magnetic material sheets 3 c , 3 e each having the first coil patterns 4 a , 4 b formed thereon and the predetermined number of the magnetic material sheets 3 d , 3 f each having the second coil patterns 5 a , 5 b formed thereon, thereby forming a laminate having the first coil conductor and the second coil conductor embedded therein.
  • the embodiment includes a firing step of firing the laminate in a firing atmosphere having an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure for Cu—Cu 2 O. Therefore, when the magnetic material sheets 3 a to 3 and the first and second coil conductors each containing Cu as the main component are fired simultaneously in a firing atmosphere having an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure for Cu—Cu 2 O, it becomes possible to produce a common mode choke coil having good insulation performance and high reliability without undergoing the reduction of Fe.
  • the ceramic green sheets 3 a to 3 i are formed from the calcined powder.
  • any other ceramic thin layer body may be used.
  • a magnetic coating film may be formed on a PET film by a printing treatment, and a coil pattern or a capacitance pattern, which is an electrically conductive film, may be formed on the magnetic coating film.
  • the first and second coil patterns 4 a , 4 b , 5 a , and 5 b are formed by screen printing.
  • this forming process is exemplary and a method according to the disclosure for producing the coil patterns is not also particularly limited. That is, other thin film formation methods such as a plating method, a transcription method, and a sputtering method may be employed for the formation of the coil patterns.
  • Fe 2 O 3 , Mn 2 O 3 , ZnO, CuO and NiO were provided as ceramic raw materials, and the ceramic raw materials were weighed precisely so that the molar contents of the ceramic raw materials became those shown in Tables 1 to 3. That is, the ceramic raw materials were weighed precisely in such a manner that the contents of ZnO and CuO were fixed to 30 mol % and 1 mol %, respectively, the molar content of each of Fe 2 O 3 and Mn 2 O 3 was varied and the remainder was made up by NiO.
  • the precisely weighed materials were placed in a pot mill made of vinyl chloride together with pure water and PSZ balls, the mixture was fully mixed and milled in a wet mode, the resultant mixture was evaporated to dryness, and the dried product was calcined at 750° C., thereby producing a calcined powder.
  • the calcined powder was placed again in the pot mill made of vinyl chloride together with a polyvinyl butyral binder (an organic binder), ethanol (an organic solvent) and PSZ balls, and the mixture was fully mixed and milled, thereby producing a ceramic slurry.
  • a polyvinyl butyral binder an organic binder
  • ethanol an organic solvent
  • the ceramic slurry was shaped into a sheet-like form having a thickness of 25 ⁇ m employing a doctor blade method, and the sheet-like material was then punched out into a size of 50 mm in length and 50 mm in width. In this manner, a magnetic material sheet was produced.
  • the oxygen partial pressure of 6.7 ⁇ 10 ⁇ 2 Pa is the equilibrium oxygen partial pressure for Cu—Cu 2 O at 1,000° C.
  • the ceramic molding was fired at the equilibrium oxygen partial pressure for Cu—Cu 2 O for 2 hours. In this manner, ring-shaped samples Nos. 1 to 104 were produced.
  • a soft copper wire was wound around each of the ring-shaped samples Nos. 1 to 104 20 turns, the inductance of the resultant product was measured at a measurement frequency of 1 MHz using an impedance analyzer (Agilent Technologies, E4991A), and a magnetic permeability ⁇ was determined from the measurement value.
  • an organic vehicle comprising terpineol (an organic solvent) and an ethyl cellulose resin (a binder resin) was mixed with a Cu powder, and the mixture was kneaded with a triple roll mill. In this manner, a Cu paste was produced.
  • the Cu paste was screen-printed on the surface of the magnetic material sheet, thereby producing an electrically conductive film having a predetermined pattern on the magnetic material sheet.
  • a predetermined number of the magnetic material sheets each having the electrically conductive film formed thereon were laminated in a predetermined order.
  • the resultant laminate was intercalated between the magnetic material sheets on each of which the electrically conductive film was not formed, and the resultant laminate was compressed and then cut into a predetermined size. In this manner, a laminated molding was produced.
  • the laminated molding was fully defatted, then the oxygen partial pressure in a firing furnace was adjusted to 6.7 ⁇ 10 ⁇ 2 Pa (the equilibrium oxygen partial pressure for Cu—Cu 2 O at 1,000° C.) by supplying an N 2 —H 2 —H 2 O mixed gas into the firing furnace, and the defatted laminated molding was introduced into the firing furnace and then fired at 1,000° C. for 2 hours. In this manner, a sintered ceramic body having the internal electrodes embedded therein was produced.
  • the sintered ceramic body was introduced into a pot together with water, and the sintered ceramic body was subjected to a barrel treatment using a centrifugal barrel machine. In this manner, a ceramic body was produced.
  • a paste for external electrode which contained Cu or the like as the main component was applied to both ends of the ceramic body and then dried.
  • the resultant product was subjected to a baking treatment at 900° C. in a firing furnace of which the oxygen partial pressure was adjusted to 4.3 ⁇ 10 ⁇ 3 Pa. In this manner, samples for the specific resistance measurement Nos. 1 to 104 were produced.
  • the oxygen partial pressure of 4.3 ⁇ 10 ⁇ 3 Pa is the equilibrium oxygen partial pressure for Cu—Cu 2 O at 900° C.
  • Each of the specific resistance measurement samples had an outer size of 3.0 mm in length, 3.0 mm in width and 1.0 mm in thickness.
  • FIG. 4 is a cross sectional view of each of the specific resistance measurement samples.
  • internal electrodes 52 a to 52 d were embedded in the magnetic material layer 53 in such a manner that the extraction sections were arranged in a staggered configuration, and external electrodes 54 a , 54 b were formed at both end surfaces of the ceramic body 51 .
  • a voltage of 50 V was applied to each of the external electrodes 54 a , 54 b for 30 seconds, and a current generated upon the application of the voltage was measured.
  • a resistivity was calculated from the measurement value, and a logarithm log ⁇ for a specific resistance (referred to hereinafter as “a specific resistance log ⁇ ”) was calculated from the outer size of each of the samples.
  • the specific resistance log ⁇ was as small as less than 7 and desired insulation performance could not be achieved, because the composition was located in the outside of the shaded area X in FIG. 1 .
  • Ceramic raw materials were weighed precisely in such a manner that the molar content of Fe 2 O 3 was 44 mol % and the molar content of Mn 2 O 3 was 5 mol % (which fall within the ranges defined in the present disclosure), the molar content of ZnO was 30 mol %, the molar content of CuO was varied, and the remainder was made up by NiO, as shown in Table 4. Except this matter, the same methods and procedures as in Example 1 were performed, thereby producing ring-shaped samples Nos. 201 to 209 and specific resistance measurement samples Nos. 201 to 209 were produced.
  • Ceramic raw materials were weighed precisely in such a manner that the molar content of Fe 2 O 3 became 44 mol %, the molar content of Mn 2 O 3 became 5 mol % and the molar content of CuO became 1 mol %, which fall within the ranges specified in the present disclosure, the molar content of ZnO was varied, and the remainder was made up by Ni, as shown in Table 5. Except this matter, the same methods and procedures as in Example 1 were performed, thereby producing ring-shaped samples Nos. 301 to 309 and specific resistance measurement samples Nos. 301 to 309 were produced.
  • the temperature dependency of saturation magnetization was determined by applying a magnetic field of 1 T (tesla) using a vibrating sample magnetometer (Toei Industry Co., Ltd.; model VSM-5-15).
  • a Curie point Tc was determined from the result of the temperature dependency of saturation magnetization.
  • the magnetic permeability ⁇ was decreased to 20 or less because the molar content of ZnO was less than 6 mol %, although the specific resistance log ⁇ and the Curie point Tc were satisfactory.
  • a common mode choke coil was produced using a magnetic material sheet having the same composition as of sample No. 1 produced in Example 1 and magnetic material sheets respectively having the same compositions as of sample Nos. 203 and 209 produced in Example 2 (see, FIGS. 2 and 3A to 3 I).
  • Cu was used as the first and second coil conductor materials to produce samples (common mode choke coils) Nos. 1′ and 203′.
  • the Cu paste which was used in Examples 1 to 3 and an electrically conductive paste containing Ag as the main component (referred to hereinafter as an “Ag paste”) were prepared.
  • Samples No. 1′, 203′ and 209′ were produced in the following manner.
  • a via hole was formed at a predetermined position on each of the magnetic material sheets of samples Nos. 1, 203 and 209 using a laser processing machine.
  • the magnetic material sheets were laminated together, and outer-covering magnetic material sheets were respectively arranged on both main surfaces of the laminate.
  • the resultant laminate was heated to 60° C., compressed by applying a pressure of 100 MPa for 60 seconds, and was then cut into a predetermined size. In this manner, laminated molding samples Nos. 1′, 203′ and 209′ were produced.
  • the laminated molding was fully defatted by heating under an atmosphere in which the oxidation of Cu did not occur, was then introduced into a firing furnace of which the atmosphere was adjusted with an N 2 —H 2 —H 2 O mixed gas so to have an oxygen partial pressure of 6.7 ⁇ 10 ⁇ 2 Pa, and was then fired at 1,000° C. for 2 hours, thereby producing a component body.
  • an electrically conductive paste for external electrodes which contained Cu as the main component was applied to side surfaces of the component body, was then dried, and was then baked in a firing furnace in which the oxygen partial pressure was adjusted to 4.3 ⁇ 10 ⁇ 3 Pa at 900° C.
  • first to fourth external electrodes were produced.
  • Each of the first to fourth external electrodes was subjected to electroplating, whereby an Ni coating film and an Sn coating film were formed sequentially on the surface of each of the first to fourth external electrodes.
  • common mode choke coil samples Nos. 1′, 203′ and 209′ were produced.
  • sample No. 209′ an electrically conductive paste for external electrodes which contained Ag as the main component was applied to side surfaces of the component body, was then dried, and was then backed in an air atmosphere at 750° C., thereby forming first to fourth external electrodes. Thereafter, as in the case of samples Nos. 1′ and 203′, each of the first to fourth external electrodes was subjected to electroplating, whereby an Ni coating film and an Sn coating film were formed sequentially on the surface of each of the first to fourth external electrodes. In this manner, a common mode choke coil sample No. 209′ was produced.
  • each of the samples thus produced had an outer size of 2.0 mm in length, 1.2 mm in width and 1.0 mm in thickness.
  • the interlayer distance between the first coil conductor and the second coil conductor was adjusted to 20 ⁇ m.
  • each of samples Nos. 1′, 203′ and 209′ was measured on an impedance value at a frequency of 100 MHz using an impedance analyzer (Agilent Technologies; E4991A).
  • sample No. 1′ had an impedance value of as low as 300 ⁇ . It is considered that this is because the specific resistance log ⁇ of sample No. 1 was as low as 2.8 and therefore the impedance value of this sample was decreased.
  • sample No. 203′ has a high impedance value of 700 to 800 ⁇ . This is because the specific resistance log ⁇ of sample No. 203 was as high as 8.2.
  • Sample No. 209′ was a sample prepared using Ag as the electrically conductive material and performing the firing in an air atmosphere. Therefore, the reduction of Fe 2 O 3 did not occur in this sample and therefore this sample had a good impedance result, i.e., an impedance value of 700 to 800 ⁇ at a measurement frequency of 100 MHz.
  • FIG. 5 illustrates the time course of the change in insulation resistance logIR
  • FIG. 6 illustrates the time course of the rate of change in resistance
  • a solid line represents the results of sample No. 203′ which is a sample of the present disclosure
  • a dashed line represents the results of sample No. 209′ which is out of the scope of the present disclosure.
  • the abscissa axis in each of FIGS. 5 and 6 represents “time (h),” the ordinate axis in FIG. 5 represents “insulation resistance logIR (R: M ⁇ ),” and the ordinate axis in FIG. 6 represents the rate of change in resistance (%).
  • an electrically conductive material containing Cu as the main component, it becomes possible to provide a ceramic electronic component, e.g., an alternately-wound common mode choke coil, which has good insulation performance and good electric properties and rarely undergoes the occurrence of migration even when the ceramic electronic component is produced by firing a magnetic material together with the electrically conductive material.
  • the molar content of Cu is 0 to 5 mol % in terms of CuO content and, when the molar content (x (mol %)) of Fe in terms of Fe 2 O 3 content and the molar content (y (mol %)) of Mn in terms of Mn 2 O 3 content are expressed by a coordinate point (x,y), the coordinate point (x,y) is located within a specific area bounded by the above-mentioned coordinate points A to H. Therefore, when the ferrite ceramic composition is fired simultaneously with a Cu-based material, the occurrence of the oxidation of Cu or the reduction of Fe 2 O 3 can be prevented, and therefore desired insulation performance can be secured without undergoing the decrease in specific resistance ⁇ .
  • the molar content of Zn is specified to 33 mol % or less in terms of ZnO content, a sufficient Curie point can be secured, and it becomes possible to produce a ceramic electronic component which can be operated under conditions including a high operation temperature.
  • the molar content of Zn is also specified to 6 mol % or more in terms of ZnO content, good magnetic permeability can be secured.
  • An embodiment of a ceramic electronic component according to the present disclosure includes a magnetic body part, a first coil conductor, and a second coil conductor which has substantially the same shape as that of the first coil conductor and of which the starting end and the terminal end are arranged with a predetermined distance apart from the first coil conductor, wherein the first coil conductor and the second coil conductor are embedded in the magnetic body part, and wherein each of the first coil conductor and the second coil conductor comprises an electrically conductive material containing Cu as the main component and the magnetic body part comprises the above-mentioned ferrite ceramic composition. Therefore, it becomes possible to produce a ceramic electronic component which can have desired good electric properties and magnetic properties and rarely undergoes migration, and can also have high reliability when the magnetic body part is fired simultaneously with the Cu-based material.
  • each of the first and second coil conductors is composed of an electrically conductive material containing Cu as the main component, even if the facing area between the first coil conductor and the second coil conductor is increased, the occurrence of migration can be avoided unlike the case in which an Ag-based material is used. Therefore, it becomes possible to produce an alternately-wound common mode choke which can exhibit good insulation resistance even when being allowed to be left for a long period under highly humid environments and has high reliability, as the ceramic electronic component.
  • the firing is performed in an atmosphere having an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure for Cu—Cu 2 O, when a magnetic body part is fired simultaneously with first and second coil conductors both comprising an electrically conductive material containing Cu as the main component, the sintering can be achieved without undergoing the oxidation of Cu and therefore it becomes possible to produce a common mode choke coil having good moisture resistance and high reliability.
  • An embodiment of a process for producing a ceramic electronic component according to the present disclosure includes a calcination step of precisely weighing an Fe compound, an Mn compound, a Cu compound, a Zn compound and an Ni compound in such a manner that the molar content of Cu becomes 0 to 5 mol % in terms of CuO content and, when the molar content (x (mol %)) of Fe in terms of Fe 2 O 3 content and the molar content (y (mol %)) of Mn in terms of Mn 2 O 2 content are expressed by a coordinate point (x,y), the coordinate point (x,y) is located within a predetermined area, mixing the weighed components together, and calcining the mixture, thereby producing a calcined powder; a ceramic thin layer body production step of producing ceramic thin layer bodies from the calcined powder; a first coil pattern formation step of forming a first coil pattern containing Cu as the main component on one of the ceramic thin layer bodies; a second coil pattern formation step of forming a second coil pattern
  • a via conductor for the second coil conductor which is electrically isolated from the first coil pattern, is formed on the surface of each of the first-coil-pattern-formed ceramic thin layer bodies and a via conductor for the first coil conductor, which is electrically isolated from the second coil pattern, is formed on the surface of each of the second-coil-pattern-formed ceramic thin layer bodies, even if the facing area between the first coil conductor and the second coil conductor is large, it becomes possible to produce an alternately-wound common mode choke coil in which the occurrence of migration can be avoided.
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JP2010018482A (ja) * 2008-07-10 2010-01-28 Tdk Corp フェライト及びその製造方法

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US10236104B2 (en) 2013-07-19 2019-03-19 Samsung Electro-Mechanics Co., Ltd. Ferrite and inductor including the same
US20150108697A1 (en) * 2013-10-22 2015-04-23 AAC Technologies Pte. Ltd. Method for producing ferrite ceramic
US9403727B2 (en) * 2013-10-22 2016-08-02 AAC Technologies Pte. Ltd. Method for producing ferrite ceramic

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